Add new debug kind LocTrackingOnly.

Summary:
This new debug emission kind supports emitting line location
information in all instructions, but stops code generation
from emitting debug info to the final output.

This mode is useful when the backend wants to track source
locations during code generation, but it does not want to
produce debug info. This is currently used by optimization
remarks (-Rpass, -Rpass-missed and -Rpass-analysis).

When one of the -Rpass flags is used, the front end will enable
location tracking, only if no other debug option is enabled.

To prevent debug information from being generated, a new debug
info kind LocTrackingOnly causes DIBuilder::createCompileUnit() to
not emit the llvm.dbg.cu annotation. This blocks final code generation
from generating debug info in the back end.

Depends on D4234.

Reviewers: echristo, dblaikie

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4235

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211610 91177308-0d34-0410-b5e6-96231b3b80d8
Objective-C. When we use @selector(save:), etc. there may be more 
than one method with mismatched type of same selector name. 
clang issues a warning to point this out since it may cause 
undefined behavior. There are cases though that some APIs 
don't care about user methods and such warnings are perceived as 
noise. This patch allows users to add paren delimiters around
selector name to turn off such warnings. So, @selector((save:)) will
turn off the warning. It also provides 'fixit' so user knows 
what to do. // rdar://16458579


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@211611 91177308-0d34-0410-b5e6-96231b3b80d8